Book bag



FIG. 1 is a front, right and top perspective view of a book bag, showing my new design;

FIG. 2 is a rear, right and top perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a top plan view thereof. 

CLAIM The ornamental design for a book bag, as shown and described. 